I'm all for pushing as many pixels as we can, but not at the expense of battery life. I'll happily take a 720p screen if it buys me even a mediocre improvement in battery life.
Is there any evidence that lower resolution screens imply an increase in battery life?
You'll find people saying this all the time, but you'll also find that it's mostly based on armchair reasoning. I'm willing to accept that higher resolution => higher GPU usage => battery usage increase, but I'm not willing to accept that this has a significant impact, not on face value. Not considering that the GPU is only heavily used in short bursts for all tasks that are not gaming, and considering that its power drain is likely still insignificant when compared to the power usage of the backlight.
A year or two ago you could compare the HTC One M7 and the Nexus 4. Two phones with very similar internals and screen size, but the HTC has a 1080p screen and was usually reviewed to have a slightly longer battery life.
I can tell you that the LG G3 required a high frequency on the ddr and bus whenever the screen is up compared to the LG G2 using the same snapdragon 800 (yea i know it's 801, not that big of a difference for this discussion).
so everything else equal you already have a higher idle current drain from the SOC side whenever screen is powered up.
Bigger screen means more power needed to light it up, but more pixels takes more computation to push the data. It probably varies how much of a factor each component is, but it's definitely both.
For two displays of different size with equal brightness showing the same image, the larger one will consume more power (at the very least (100% efficiency), the display will consume the amount of energy contained in the photons that are radiated out from each pixel).
But a larger screen won't necessarily require much more computation. Imagine showing photos, for example. The increased size of the memory copy (from disk to RAM to GPU), won't consume much more power, I would think.
And if it does, it will only be when loading the image to show it on the screen. After this is over, it will sit idle until loading the next image (consuming no additional power from use of CPU/GPU/storage).
For games, though, you're right. A higher resolution display will make a larger difference in CPU/GPU/storage power use, especially if the CPU is used, since the GPU is probably designed for a higher resolution display.
The Huawei Mate 2 has a 6" screen, 720p, and gets about 2 days (almost 40 hours) of battery. Unfortunately, they have a screwed up copy of 4.3, and it is really terrible and Huawei doesn't release enough info to make Cyanogen work on it.
Yes but all else equal, lower resolution screens will have better battery life. They require dimmer backlights to achieve the same brightness level, and the graphics hardware doesn't have to work as hard (or be as powerful). For phones, resolution starts running into diminishing returns around 300ppi. The Nexus 6's 493ppi sacrifices significant battery life for practically unnoticeable resolution improvements.
Phones with larger screen's generally have better battery life than phones with smaller screens. Look at the iphone 6 vs 6+ for instance. Increasing the screen size leads to disproportionately more room for battery since most of the other components dont get bigger as the screen size does.
I agree that we are at a time when battery life should be prioritized, but I would prefer that to come from thickness. Increasing the thickness by just 25% or so would allow a much larger battery.
We're not necessarily arguing against screen size, but pixel density. That is, instead of scaling the resolution linearly with the screen size, they did that and some. So now instead of a low 400s pixel density range like the Nexus 5, the Nexus 6 sits at a de facto PPI of roughly 500.
Obviously there's a cost to this, both in battery and hardware requirements to push those extra pixels. Meanwhile nobody can detect pixels on a Nexus 5, but apparently it wasn't good enough.
And next year we'll see PPI at 500-600. I just don't get it.
As for thickness, I think the Nexus does quite well. It's about 50% thicker than the iPhone 6 which is a great number (~10mm) to be at in my opinion.
additionally, no one can seem to detect the difference in battery life between 1080p and 1440p. Without having stronger data I have to lean towards the backlight taking up enough power that the difference in cpu/gpu work makes little to no difference.
Agreed, but what "feature" does a 1080p display provide over a 720p one? The smartphone/dumbphone comparison doesn't really work - there are no new features here.
Say I forget to charge my phone during 20% of the nights. A battery that lasts a single day will fail me very often compared to a two-day battery. Not to mention that unlike "dumb" phones, the iPhone won't turn itself on automatically to wake me up in the morning.
Also, battery life is measured for "normal use". If you are draining your phone eg. by using it for directions in a friend's car without a charger, then it's suddenly more like 4 hours of battery life.
